Nonlinear and linear numerical models have been used to investigate lee-wave induced rotor formation downwind of mountains. Results from both idealised and case-study simulations will be presented. In the latter case, the model predictions are compared with detailed field observations of rotors which were made between November 2000 and October 2001 on East Falkland in the south Atlantic.

Field measurements on East Falkland reveal that during rotor events a strong downslope wind occurs on the lee side of the mountains and this wind field is highly turbulent and contains localised regions of flow acceleration and deceleration. The wind direction is also highly variable to the lee of the mountains and regions of strong convergence occur, implying flow separation. The measurements indicate that the occurrence of rotors is sensitive to the existence of a strong (up to 10 K) temperature inversion upwind, which occurs at around the mountain height. Idealised numerical simulations will be used to investigate this result. In particular, the effect of the height and magnitude of the inversion on the strength of the rotor vorticity and turbulence intensity will be examined.